The former SSAA message board was monitored by the NSW police.
The IPSC Australia BBS was (probably still is) monitored by the federal attorney generals department.
Shooters who have advertised barrels on Ebay Australia have been arrested.
Shooters who have used email to order parts from the States without obtaining the necessary permits have been busted, one was arrested for ordering a how to make your own machine gun book.
A shooter who obtained an import permit for a part for a Cobray pistol, which was registered to his name, was arrested and convicted for importing the part, even though the govt had given him a permit to do so.
There is no constitutional right to privacy or free speech in this country, warrants for computer hacking and wiretapping are issued by the attorney general, not a judge.He has a group in his office whose sole job is to make life difficult for shooters. So expect your electronic communications to be monitored. If they aren't then no foul. if they are then you will have modified your behaviour to stay within the law and again, no foul.
There is at least one NSW cop on this forum, and I believe one QLD cop as well.
Personally, I see no value in breaking the law, however asinine it is, as my freedom to own BB machine guns is less important than my freedom to walk around in the sun.
Get yourself a dealers licence and you can make anything you want and you can buy and sell the real thing. Dealers can legally manufacture and possess heavy machine guns, short barrelled pistols, sub guns, rocket launchers and semi auto rifles. The market for them is small, but stocking (collecting) and testing and evaluating (shooting) them is one of the few perks of being in the gun trade. Profitability sure isn't.
As for nerf guns, they are probably an illegal import, just like airsoft.